Terrestrial resources show obvious signs of exhaustion. By the end of the century man will have to turn towards the oceans to obtain a large proportion of his requirements in respect of food, energy, and mineral deposits.
The size of reserves of polymetallic nodules lying on ocean beds is out of all proportion to that of terrestrial reserves of known precious minerals.
Among processes contemplated for collecting these nodules, some have not yet got beyond the conception stage. Nevertheless, two methods of working have reached the phase of experiments at sea. One consists in gathering together the nodules on the bed and introducing them into a lifting pipe connecting the collecting machine on the ocean bed to the storage unit on the surface or submerged near the surface. The other is based on dredging by means of an immsense loop which rotates continuously and to which buckets or scoops are attached on the noria principle.
The practical application of either of these methods, based on a platform situated in the sea, encounters the difficulties due to the great depth at which the substantial deposits known as the present time are situated, this depth usually being of the order of four to six thousand meters.
The deposits which will be worked first are those which are situated on substantially flat beds, which are usually composed of viscous, sticky clay.
This nature of the ocean beds makes it difficult if not impossible to use vehicles equipped with wheels, caterpillar tracks, or sledges which have already been conceived for working at shallow depth.